The present invention relates to the biomedical arts, particularly implantable cuffs. The present invention finds application in electrodes disposed around nerve trunks and other small tissue strands and will be described with reference thereto. It is to be appreciated that the invention is also applicable to medicinal infusers and other implanted biomedical devices for introducing, monitoring, or removing matter or energy.
Functional electrical stimulation of the nervous system has been shown in recent years to offer great hope in restoring some degree of lost sensory and motor function in stroke victims and individuals with spinal cord lesions. Ways in which functional electrical stimulation can be utilized to restore a particular function include: (1) the use of surface electrodes to activate the nerves in the general region of interest; (2) the use of intramuscular electrodes, also to activate the nerves in a general region; and (3) the use of nerve cuff electrodes placed around specific nerves of interest and used to activate them specifically. The third alternative offers advantages over the first two in that it requires the least amount of stimulating current and hence charge injected into the tissue. In addition, it allows easy excitation of entire muscles rather than parts of muscles, a common situation for the first two categories. Because the use of nerve cuff electrodes requires delicate surgery, they are usually contemplated only when: (1) excitation of specific, isolated muscles is desired; or (2) the generation of unidirectional action potentials is required.
The prior art cuff electrodes included a cylinder of dielectric material defining a bore therethrough of sufficient diameter to receive the nerve trunk to be electrically stimulated. The cylinder had a longitudinal split or opening for receiving a nerve. During installation, the longitudinal split was sutured or otherwise held closed. Although suturing held the cuff in place, an electric current path was defined through the split which permitted current leakage. Two or three annular electrodes were positioned on the inner surface of the bore for use in applying the electrical stimuli. The electric stimuli, for example, may provide functional electrical stimulation, may block natural nerve pulses traveling along the nerve trunk, or the like.
The present invention contemplates a new and improved cuff which is readily installed and removed without damaging the nerve trunk or other tissue.